/*
 * Copyright 2021 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package androidx.compose.runtime.saveable

/**
 * The [Saver] implementation which allows to represent your class as a map of values which can be
 * saved individually.
 *
 * What types can be saved is defined by [SaveableStateRegistry], by default everything which can be
 * stored in the Bundle class can be saved.
 *
 * You can use it as a parameter for [rememberSaveable].
 *
 * @sample androidx.compose.runtime.saveable.samples.MapSaverSample
 */
public fun <T> mapSaver(
    save: SaverScope.(value: T) -> Map<String, Any?>,
    restore: (Map<String, Any?>) -> T?,
): Saver<T, Any> =
    listSaver<T, Any?>(
        save = {
            mutableListOf<Any?>().apply {
                save(it).forEach { entry ->
                    add(entry.key)
                    add(entry.value)
                }
            }
        },
        restore = { list ->
            val map = mutableMapOf<String, Any?>()
            check(list.size.rem(2) == 0) { "non-zero remainder" }
            var index = 0
            while (index < list.size) {
                val key = list[index] as String
                val value = list[index + 1]
                map[key] = value
                index += 2
            }
            restore(map)
        },
    )
